Understanding Rhampholeon Genus and Its Evolution

The Rhampholeon genus is a group of small, burrowing lizards that are native to the tropical forests of sub-Saharan Africa. They are also known as dwarf chameleons.

These lizards are relatively small, with most species reaching a length of about 3-4 inches. They have a unique appearance, with a flattened head and a long, pointed snout.

One of the most interesting things about Rhampholeon lizards is their ability to live underground, where they can escape predators and regulate their body temperature. In the wild, they are often found in areas with loose soil or sand, where they can easily dig burrows.

As we'll explore in more detail, the evolution of the Rhampholeon genus is closely tied to their underground lifestyle.

The genus Rhampholeon is a group of small chameleons found in various parts of Africa. It was first described by Albert Günther in 1874.

The genus Rhampholeon includes 25 recognized species. These species are found in countries such as Tanzania, Mozambique, Malawi, and Democratic Republic of the Congo.

Some of the species within the genus Rhampholeon include Rhampholeon boulengeri, Rhampholeon bruessoworum, and Rhampholeon marshalli. These species have unique characteristics, such as their color patterns and distribution ranges.

Here are some of the species within the genus Rhampholeon, along with their common names and distribution ranges:

Note: This is not an exhaustive list of all the species within the genus Rhampholeon.

The genus Rhampholeon GÜNTHER, 1874 is a fascinating group of lizards. It was first described by Albert Günther in 1874.

Some of the earliest known species within this genus include Rhampholeon spectrum and Rhampholeon spinosus, both of which were described in the late 19th century. Rhampholeon spectrum was originally described in a different genus, but was later reclassified as part of Rhampholeon.

The genus Rhampholeon is comprised of many species, including Rhampholeon boulengeri, Rhampholeon bruessoworum, and Rhampholeon marshalli. These species can be found in various parts of Africa, including Mozambique, Tanzania, and Zimbabwe.

Here's a list of some of the species within the genus Rhampholeon:

In recent years, new species have been discovered within the genus Rhampholeon. For example, Rhampholeon monteslunae was described in 2024, and Rhampholeon nicolai, Rhampholeon sabini, and Rhampholeon waynelotteri were also described in the same year. These discoveries highlight the ongoing research and exploration of this fascinating genus.

The Acuminatus species is a fascinating addition to the Genus Rhampholeon. It's one of the smallest chameleons, with a snout-to-vent length (SVL) of 47-57 mm and a maximum total length (TL) of 82 mm.

One of the distinctive features of the Acuminatus is its large, discoid, and vertically flattened rostral process, which projects forward off the rostrum. This process can be up to 5 × 3 mm in size.

This species is found in Tanzania, specifically in the Nguru mountains, at an elevation of 1500-1600 meters. The type locality is near the village of Ubili.

The Acuminatus is oviparous, meaning it lays eggs. Unfortunately, not much is known about its abundance, as it was only described in one original study.

The name Acuminatus comes from the Latin word "acuminare", which means "to sharpen." This refers to the numerous sharp spines found on the head and body of this species.

The split between the Rhampholeon species complex from West-Central Africa and the montane endemic clade from the Eastern Arc Mountains of Tanzania occurred around 40 million years ago in the Eocene.

This ancient split led to the divergence of several lineages, including the lowland and montane clades within R. spectrum, which occurred around 11.1 million years ago in the mid-Miocene.

Taxon sampling was crucial in this phylogenetic analysis, and researchers obtained samples from various locations in Cameroon, Gabon, and Equatorial Guinea.

Samples were collected from field expeditions to Cameroon between January 2017 and August 2018.

Genetic sequences from three additional samples were drawn from records in GenBank and used only in analysis of Sanger-sequenced data.

New samples came from several sites in Cameroon, including Mt. Cameroon, Mt. Manengouba, Mt. Nlonako, Mt. Kupe, and Korup National Park.

A total of 25 individuals were collected from Cameroon, with the highest number coming from Korup National Park with 9 individuals.

Similar sites in Gabon and Equatorial Guinea were also sampled, including Ivindo, Mekambo, and Bioko Island.

Voucher specimens are deposited in the herpetology collection of the University of Kansas and the California Academy of Science.

We sequenced genome-wide anonymous nuclear markers for 28 individuals using a modified version of the ddRADseq protocol. This involved library prep and pooling, followed by sequencing on one Illumina HiSeqX Lane at Novogene.

The Illumina reads from the ddRAD were processed using STACKS v2.5, a powerful tool for de novo assembly of ddRADseq data. This allowed us to recover putative single-copy, orthologous loci.

We tested a range of assembly parameters in STACKS to optimize recovery of SNPs, with parameters such as the maximum number of gaps allowed between nucleotides and the number of mismatches allowed in the alignment between samples being modified. This was done to ensure the optimal de novo assembly of ddRADseq data.

The final dataset used a combination of parameters that produced the most SNPs without loss in depth of coverage across loci. This was achieved by adjusting parameters such as M, n, r, and p in STACKS.

Phylogenetic relationships reveal the history of how species are related to each other. The split between the R. spectrum species complex from West-Central Africa and the montane endemic clade from the Eastern Arc Mountains of Tanzania occurred in the Eocene ~40 Mya.

The R. spectrum species complex has undergone significant diversification over time. Within R. spectrum, the divergence between the lowland and montane clades occurred around the mid-Miocene ~11.1 Mya.

This mid-Miocene divergence was followed by the separation of the Bioko population from the continental CVL ~9.3 Mya. The initial divergence between the two lowland populations (Gabon and Korup) is estimated to have occurred in the late Miocene (~6.9 Mya).

The earliest divergence within the CCVL lineage happened during the Miocene-Pliocene transition (~5.2 Mya) and produced the Mt. Cameroon population and the Kupe, Nlonako, and Manengouba populations. All five newly discovered lineages within R. spectrum arose between the middle- and late-Miocene.

A Bayesian chronogram of the Pygmy Chameleon genus Rhampholeon shows the estimated ages of different nodes in millions of years. Numbers near nodes denote the median value of node age in millions of years.

Rhampholeon spectrum has four distinct populations: CCVL, Bioko, Korup, and Gabon.

These populations are supported by demographic modeling, which suggests that divergence with secondary contact is the most likely demographic scenario.

Temperature oscillations and habitat contraction during the Pliocene-Pleistocene likely contributed to this demographic scenario.

The shallow channel between Bioko Island and continental Africa, averaging only 60 m deep, facilitated gene flow between divergent lineages/species.

Sea levels dropped ≥ 100 m during the Last Glacial Maximum, and similar changes occurred several times during the Ice Age.

Rhampholeon spectrum's species distribution model shows stability at high elevation over the last 22,000 years.

The suitable habitat identified in the heart of the Congo suggests that a paucity of genetic material from this region may be to blame for the inferred lack of Eocene–Miocene diversification.

Topologically complex mountains with pronounced geodiversity, like those found in Rhampholeon's habitat, may be correlated with high levels of biodiversity.

Three major population contractions of Rhampholeon spectrum have been identified, and their geographic locations overlap with hypothesized refugia.

Demographic modeling of Rhampholeon spectrum has identified four distinct populations: CCVL, Bioko, Korup, and Gabon. These populations have undergone divergence with secondary contact, which is supported by temperature oscillations and habitat contraction during the Pliocene-Pleistocene.

The shallow channel between Bioko Island and continental Africa, averaging only 60 m deep, allowed for gene flow between divergent lineages during periods of low sea levels. This is evident from the Last Glacial Maximum, where global sea levels dropped ≥ 100 m.

Our species distribution model shows that Rhampholeon spectrum has been stable at high elevations for the last 22,000 years. This is consistent with the idea that topologically complex mountains support high levels of biodiversity.

Three major population contractions have been identified, and their geographic locations overlap with hypothesized refugia. The suitable habitat identified in the heart of the Congo suggests that a lack of genetic material from this region may be responsible for the inferred lack of Eocene–Miocene diversification.

The suitable habitat for Rhampholeon spectrum during the mid-Holocene and last glacial maximum is shown in Figure S5. The darkest green indicates agreement between all three global climate models (GCMs), while the lightest green shows support from only one GCM.

A stability map representing suitable habitat for Rhampholeon spectrum persistent across LGM and current climate regimes is also shown in Figure S5. Dark green represents the highest habitat stability inferred.

Five new Rhampholeon species have been discovered in the Rhampholeon boulengeri complex.

The new species were identified through genetic analyses of over 130 pygmy chameleons from more than 20 different locations.

The complex inhabits various habitats along the Albertine Rift, a 6000 km long chain of mountains and rifts stretching from Lake Albert in Uganda to Lake Tanganyika.

Rhampholeon plumptrei was named in honour of Andrew Plumptre, an English zoologist who has been campaigning for species conservation along the African Rift Valley for almost 20 years.

Rhampholeon plumptrei lives in montane and submontane rainforest at altitudes of 1203-2269 metres, and has a clearly visible nasal appendage and a slightly shorter tail than Rhampholeon boulengeri.

The males of this species have a white colouration on the throat and belly and one or two diagonal dark stripes on the body.

The Eastern Arc Mountains of Tanzania are home to a remarkable diversity of pygmy chameleons, with six new species of Rhampholeon discovered in the region.

These new species were identified through a combination of descriptive morphology and phylogenetic analysis, highlighting the importance of genetics in distinguishing between species.

The Uzungwa Scarp Nature Reserve is home to Rhampholeon colemani, one of the newly described species.

Morphometric variation between species is surprisingly limited, making it challenging to distinguish between them based on physical characteristics alone.

The Rubeho Mountains are home to Rhampholeon rubeho, another newly discovered species.

The Eastern Arc Mountains contain more species of chameleons than any other area in mainland Africa, making them a hotbed of biodiversity.

Rhampholeon uluguruensis, or the Uluguru Pygmy Chameleon, is one of the many species found in the region.

The export market for live specimens has made some species popular, putting them at risk of decline due to overcollection.

The forest patches of the Eastern Arc Mountains are relatively small, covering less than 3000 km2, yet they contain an extraordinary number of species.

Rhampholeon moyeri, or Moyer's Pygmy Chameleon, is another species found in the region.

On a similar theme: Malagasy Giant Chameleon

Two distinct mechanisms explain the contemporary phylogeographic patterns of R. spectrum: vicariance on the African continent and dispersal via ephemeral land bridges toward the continental island of Bioko.

The mid-Eocene subdivision of sub-Saharan rainforest into small patches likely initiated forest fragmentation-induced vicariance within Rhampholeon.

The diversification of R. spectrum into two main lineages during the mid-Miocene corresponds with the uplift of the Cameroon Volcanic Line.

We found evidence to support the presence of two to five distinct species within our data set.

More genetic sampling will be needed to develop a full picture of the genetic structure of R. spectrum in South-East Cameroon, the Republic of Congo, and farther west.

Our work represents one of a few recently emerging studies considering alternate processes of diversification and potentially speciation in the Lower Guinean Forest and adjacent islands in the Gulf of Guinea.

Newly-elucidated, geographically-based genomic variation across the range of an endemic, previously unstudied forest-associated vertebrate enables a comprehensive understanding of the temporal and evolutionary context of putative speciation in a unique forest vertebrate from a celebrated biodiversity hotspot.

A taxonomic follow-up study using morphology, ecology, and characterizations of gene flow could help determine if the genetic lineages observed provide actual statistically robust support for separate species recognition.